This week, Dr. Sydney Spiesel discusses whether sex late in pregnancy makes women go into labor, the link for kids between being overweight and getting too little sleep, and the risk of serious blood clots during air travel.
Question: Does sex late in pregnancy set off labor? A lot of folklore says it does and, for that reason, some obstetricians warn their patients against it. There are good scientific arguments to make us expect that the idea might be true. For instance, prostaglandin E., an ingredient of semen, stimulates uterine contraction and can start labor. So can breast stimulation, and orgasm while having sex during pregnancy increases uterine activity.
Context: Actually, it would be very desirable if sex did play this role. For sound medical reasons—usually to protect the fetus from the negative effects of more than 42 weeks gestation or from the problems associated with maternal diabetes—doctors now use artificial means to stimulate the onset of labor. The artificial methods are amniotomy ("breaking of the waters") and medications that stimulate contractions. But there are certain disadvantages: a higher rate of cesarean sections, forceps-assisted delivery, bleeding after delivery, and prolonged labor. In addition, by several different measures, the babies on average don't do quite as well.
New study: If having sex late in pregnancy proved to be an effective natural method of starting off labor, it might be superior to the artificial methods (and many women might prefer it). Three obstetricians at the University of Malaysia set out to explore this question by recruiting a group of about 200 women late in pregnancy, chosen because they were all scheduled to be induced within the week if they didn't spontaneously go into labor. Half the women were actively encouraged to have vaginal sex, and the remaining half—the control group—were neither encouraged nor discouraged.
Findings: About 60 percent of the women encouraged to have sex did so, compared with only 40 percent of the control group. So, did this increased rate of rowdiness trigger more spontaneous labor? Nope. The rate was virtually the same in both groups, as was the likelihood of complications like maternal fever, cesarean section, excess bleeding, or evidence of increased newborn stress or other problems.
Conclusion: Given these findings, then, there is no particular reason to recommend sex late in pregnancy as a way of averting artificial induction of labor. But the study suggests that there is a different benefit: pleasure. Of the women in both groups who reported having sex in the last week of pregnancy, more than 80 percent said they had an orgasm.
Question: Several large studies, both here and abroad, have established a clear association in adults between inadequate sleep and obesity. The less we sleep at night on average, the more overweight we are likely to be. Does this same relationship hold for children? A number of small studies have hinted that this is likely to be the case, but, to date, the research has been flawed.
New study: Now comes a carefully done study by Dr. Julia Lumeng of the University of Michigan and her colleagues. The data were drawn from a large National Institute of Child Health and Human Development study, beginning in 1991, that includes more than 1,000 children in 10 areas of the United States, urban and rural. The children were tracked from birth through sixth grade. The children's height and weight were measured when they were in third grade and again when they were in sixth grade. Demographic data on race, socioeconomic status, and gender were also collected because these factors are also known to be associated with the prevalence of obesity, and it was important to separate out those effects from the consequences of inadequate sleep.